Electrical circuit means for manually adjustable apparatus and system for selectively controlling the air-fuel ratio supplied to a combustion engine

ABSTRACT

A vehicle has a combustion engine, ground-engaging drive wheels, an induction passage for supplying motive fluid to the engine, a fuel metering system communicating generally between a source of fuel and the induction passage, a valving arrangement in the fuel metering system effective to controllably alter the rate of metered fuel flow through the fuel metering system; an oscillator electrically connected to the valving arrangement intermittently energizes the valving arrangement, and a manually controlled adjustment selectively alters the operation of the oscillator to selectively vary the respective percentages of times that the valving arrangement is energized and de-energized by the oscillator.

FIELD OF THE INVENTION

This invention relates generally to fuel metering systems for use withcombustion engines and more particularly to a fuel metering systemwherein the rate of flow of metered fuel can be manually selected asduring actual engine operation.

BACKGROUND OF THE INVENTION

Even though the automotive industry has over the years, if for no otherreason than seeking competitive advantages, continually exerted effortsto increase the fuel economy of automotive engines, the gainscontinually realized thereby have been deemed by various levels ofgovernments to be insufficient. Further, such levels of government havealso imposed regulations specifying the maximum permissible amounts ofcarbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NO_(x))which may be emitted by the engine exhaust gases into the atmosphere.

Unfortunately, the available technology employable in attempting toattain increases in engine fuel economy is, generally, contrary to thattechnology employable in attempting to meet the governmentally imposedstandards on exhaust emissions.

For example, the prior art, in trying to meet the standards for NO_(x)emissions, has employed a system of exhaust gas recirculation whereby atleast a portion of the exhaust gas is re-introduced into the cylindercombustion chamber to thereby lower the combustion temperature thereinand consequently reduce the formation of NO_(x).

The prior art has also proposed the use of engine crankcaserecirculation means whereby the vapors which might otherwise becomevented to the atmosphere are introduced into the engine combustionchambers for burning.

The prior art has also proposed the use of fuel metering means which areeffective for metering a relatively overly-rich (in terms of fuel)fuel-air mixture to the engine combustion chamber means as to therebyreduce the creation of NO_(x) within the combustion chamber. The use ofsuch overly rich fuel-air mixtures results in a substantial increase inCO and HC in the engine exhaust, which, in turn, requires the supplyingof additional oxygen, as by an associated air pump, to such engineexhaust in order to complete the oxidation of the CO and HC prior to itsdelivery into the atmosphere.

The prior art has also heretofore proposed retarding of the engineignition timing as a further means for reducing the creation of NO_(x).Also, lower engine compression ratios have been employed in order tolower the resulting combustion temperature within the engine combustionchamber and thereby reduce the creation of NO_(x).

The prior art has also proposed the use of fuel metering injection meansinstead of the usually-employed carbureting apparatus and, undersuperatmospheric pressure, injecting the fuel into either the engineintake manifold or directly into the cylinders of a piston type internalcombustion engine. Such fuel injection system, besides being costly,have not proven to be generally successful in that the system isrequired to provide metered fuel flow over a very wide range of meteredfuel flows. Generally, those injection system which are very accurate atone end of the required range of metered fuel flows, are relativelyinaccurate at the opposite end of that same range of metered fuel flows.Also, those injection systems which are made to be accurate in themid-portion of the required range of metered fuel flows are usuallyrelatively inaccurate at both ends of that same range. The use offeedback means for altering the metering characteristics of a particularfuel injection system have not solved the problem because the problemusually is intertwined with such factors as: effective aperture area ofthe injector nozzle; comparative movement required by the associatednozzle pintle or valving member; inertia of the nozzle valving memberand nozzle "cracking" pressure (that being the pressure at which thenozzle opens). As should be apparent, the smaller the rate of meteredfuel flow desired, the greater becomes the influence of such factorsthereon.

It is anticipated that the said various levels of government willestablish even more stringent exhaust emission limits and even higherstandards of fuel economy.

The prior art, in view of such anticipated requirements with respect toNO_(x), has suggested the employment of a "three-way" catalyst, in asingle bed, within the stream of exhaust gases as a means of attainingsuch anticipated exhaust emission limits. Generally, a "three-way"catalyst (as opposed to the "two-way" catalyst system also well known inthe prior art) is a single catalyst, or catalyst mixture, whichcatalyzes the oxidation of hydrocarbons and carbon monoxide and also thereduction of oxides of nitrogen. It has been discovered that adifficulty with such a "three-way" catalyst system is that if the fuelmetering is too rich (in terms of fuel), the NO_(x) will be reducedeffectively, but the oxidation of CO will be incomplete. On the otherhand, if the fuel metering is too lean, the CO will be effectivelyoxidized but the reduction of NO_(x) will be incomplete. Obviously, inorder to make such a "three-way" catalyst system operative, it isnecessary to have very accurate control over the fuel metering functionof associated fuel metering supply means feeding the engine. Ashereinafter described, the prior art has suggested the use of fuelinjection means with associated feedback means (responsive to selectedindicia of engine operating conditions and parameters) intended tocontinuously alter or modify the metering characteristics of the fuelinjection means. However, at least to the extent hereinafter indicated,such fuel injection systems have not proven to be successful.

It has also heretofore been proposed to employ fuel metering means, of acarbureting type, with closed loop feedback means responsive to thepresence of selected constituents comprising the engine exhaust gases.Such closed loop feedback means were employed to modify the action of amain metering rod of a main fuel metering system of a carburetor.However, tests and experience have indicated that such a prior artcarburetor with such a related closed loop feedback means could notprovide the degree of accuracy required in the metering of fuel to anassociated engine as to assure meeting, for example, the saidanticipated emission and fuel economy standards.

Also, heretofore, the prior art has proposed an arrangement whereby acarburetor, having an induction passage therethrough with a venturitherein and a main fuel discharge nozzle situated generally within theventuri, has a main fuel metering system communicating generally betweena fuel reservoir and the main fuel discharge nozzle along with an idlefuel metering system communicating generally between a fuel reservoirand said induction passage at a location generally in close proximity toan edge of a variably openable throttle valve situated in the inductionpassage downstream of the main fuel discharge nozzle. Modulating valvingmeans are provided to controllably alter the rate of metered fuel flowthrough each of the main and idle fuel metering systems in response tocontrol signals generated as a consequence of selected indicia of engineoperation. Such indicia comprised engine exhaust gas constituentresponsive means for sensing the relative percentage of selected exhaustgas constituents and producing control signals in response thereto.Also, electronic computer means are usually provided for processing allof the control signals and, in response thereto, producing an outputsignal or signals effective for controlling the modulating valvingmeans.

In the main, such prior art systems can not be readily adapted to allengines and vehicles especially where such engines and/or vehicles weremanufactured prior to the commercial availability of such prior art fuelmetering systems.

Accordingly, the invention as herein disclosed is primarily directed tothe provision of a fuel metering system and electrical circuit meanswhich can be readily adapted to all engines and vehicles and which,further, enables the vehicle operator a certain degree of controlthereover in order to be able to select, for example, the rate ofmetered fuel flow to the engine in order to obtain maximum fuel economyfor whatever engine demands are being then experienced.

SUMMARY OF THE INVENTION

According to the invention electrical circuit means for a fuel meteringsystem for a vehicle having a combustion engine, ground-engaging drivewheel means, passage means for supplying motive fluid to said engine, asource of fuel, fuel metering system means communicating generallybetween said source of fuel and said induction passage means,selectively controlled modulating valving means effective tocontrollably alter the rate of metered fuel flow through said fuelmetering system means comprises oscillator means electrically connectedto said valving means for intermittently energizing said valving means,and manually controlled adjustment means for selectively altering theoperation of said oscillator means to selectively vary the respectivepercentages of times that said valving means is energized anddeenergized by said oscillator means.

Various general and specific objects, advantages and aspects of theinvention will become apparent when reference is made to the followingdetailed description considered in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein for purposes of clarity certain details and/orelements may be omitted from one or more views:

FIG. 1 illustrates, in side elevational view, a fragmentary portion of avehicle equipped with a vehicular combustion engine employing acarbureting apparatus and related control system employing teachings ofthe invention;

FIG. 2 is an enlarged view, in cross-section, of the carburetingapparatus of FIG. 1;

FIG. 3 is an enlarged axial cross-sectional view of one of the elementsshown in FIG. 2 with fragmentary portions of related structure alsoshown in FIG. 2.

FIG. 4 is a cross-sectional view taken generally on the plane of line4--4 of FIG. 3 and looking in the direction of the arrows;

FIG. 5 is a graph illustrating, generally, fuel-air ratio curvesobtainable with structures employing teachings of the invention; and

FIG. 6 is a schematic wiring diagram of circuitry employing teachings ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the drawings, FIG. 1 illustrates acombustion engine 10 used to propell an associated vehicle as throughpower output transmission means 12, drive or propeller shaft 13,differential gearing assembly 14, drive axle means 15 and groundengaging drive wheels 17 and 19. The engine 10 may, for example, be ofthe internal combustion type employing, as is generally well known inthe art, a plurality of power piston means therein. As generallydepicted, the engine assembly 10 is shown as being comprised of anengine block 21 containing, among other things, a plurality of cylindersrespectively reciprocatingly receiving said power pistons therein. Aplurality of spark or ignition plugs 16, as for example one for eachcylinder, are carried by the engine block and respectively electricallyconnected to an ignition distributor assembly or system 18 operated intimed relationship to engine operation.

As is generally well known in the art, each cylinder containing a powerpiston has exhaust aperture or port means and such exhaust port meanscommunicate as with an associated exhaust manifold which isfragmentarily illustrated in hidden line at 20. Exhaust conduit means 22is shown operatively connected to the discharge end 24 of exhaustmanifold 20 and leading as to the rear of the associated vehicle for thedischarging of exhaust gases to the atmosphere.

Further, as is also generally well known in the art, each cylinder whichcontains a power piston also has inlet aperture means or port means andsuch inlet aperture means communicate as with an associated inletmanifold which is fragmentarily illustrated in hidden line at 26.

As generally depicted, a carbureting type fuel metering apparatus 28 issituated atop a cooperating portion of the inlet or intake manifoldmeans 26. A suitable inlet air cleaner assembly 30 may be situated atopthe carburetor assembly 28 to filter the air prior to its entrance intothe inlet of the carburetor 28.

FIG. 2 illustrates a fuel metering apparatus, such as a carburetor 28,as comprising a main carburetor body 32 having induction passage means34 formed therethrough with an upper inlet end 36, in which generally issituated a variably openable choke valve 38 carried as by a pivotalchoke shaft 40, and a discharge end 42 communicating as with the inlet44 of intake manifold 26. A venturi section 46, having a venturi throat48, is provided within the induction passage means 34 generally betweenthe inlet 36 and outlet or discharge end 42. A main metering fueldischarge nozzle 50, situated generally within the throat 48 of venturisection 46, serves to discharge fuel, as is metered by the main meteringsystem, into the induction passage means 34.

A variably openable throttle valve 52, carried as by a rotatablethrottle shaft 54, serves to variably control the discharge and flow ofcombustible (fuel-air) mixtures into the inlet 44 of intake manifold 26.Suitable throttle control linkage means, as generally depicted at 56, isprovided and operatively connected to throttle shaft 54 in order toaffect throttle positioning in response to vehicle operator demand.

Carburetor body means 32 may be formed as to also define a fuelreservoir chamber 58 adapted to receive, as through inlet means 59, andcontain fuel 60 therein the level of which may be determined as by, forexample, a float operated fuel inlet valve assembly, as is generallywell known in the art.

The main fuel metering system comprises passage or conduit means 62communicating generally between fuel chamber 58 and a generally upwardlyextending main fuel well 64 which, as shown, may contain a main welltube 66 which, in turn, is provided with a plurality of generallyradially directed apertures 68 formed through the wall thereof as tothereby provide for communication as between the interior of the tube 66and the portion of the well 64 generally radially surrounding the tube66. Conduit means 70 serves to communicate between the upper part ofwell 64 and the interior of discharge nozzle 50. Air bleed type passagemeans 72, comprising conduit means 74 and calibrated restriction ormetering means 76, communicates as between a source of filtered air andthe upper part of the interior of well tube 66. A main calibrated fuelmetering restriction 78 is situated generally upstream of well 64, asfor example in conduit means 62, in order to meter the rate of fuel flowfrom chamber 58 to main well 64. As is generally well known in the art,the interior of fuel reservoir chamber 58 is preferably pressure ventedto a source of generally ambient air as by means of, for example,vent-like passage means 80 leading from chamber 58 to the inlet end 36of induction passage 34.

Generally, when the engine is running, the intake stroke of each powerpiston causes air flow through the induction passage 34 and venturithroat 48. The air thusly flowing through the venturi throat 48 createsa low pressure commonly referred to as a venturi vacuum. The magnitudeof such venturi vacuum is determined primarily by the velocity of theair flowing through the venturi and, of course, such velocity isdetermined by the speed and power output of the engine. The differencebetween the pressure in the venturi and the air pressure within fuelreservoir chamber 58 causes fuel to flow from fuel chamber 58 throughthe main metering system. That is, the fuel flows through meteringrestriction 78, conduit means 62, up through well 64 and, after mixingwith the air supplied by the main well air bleed means 72, passesthrough conduit means 70 and discharges from nozzle 50 into inductionpassage means 34. Generally, the calibration of the various controllingelements are such as to cause such main metered fuel flow to start tooccur at some pre-determined differential between fuel reservoir andventuri pressure. Such a differential may exist, for example, at avehicular speed of 30 m.p.h. at normal road load.

Engine and vehicle operation at conditions less than that required toinitiate operation of the main metering system are achieved by operationof the idle fuel metering system, which may not only supply metered fuelflow during curb idle engine operation but also at off idle operation.

At curb idle and other relatively low speeds of engine operation, theengine does not cause a sufficient rate of air flow through the venturisection 48 as to result in a venturi vacuum sufficient to operate themain metering system. Because of the relatively almost closed throttlevalve means 52, which greatly restricts air flow into the intakemanifold 26 at idle and low engine speeds, engine or intake manifoldvacuum is of a relatively high magnitude. This high manifold vacuumserves to provide a pressure differential which operates the idle fuelmetering system.

Generally, the idle fuel system is illustrated as comprising calibratedidle fuel restriction metering means 82 and passage means 83communicating as between a source of fuel, as within, for example, thefuel well 64, and a generally upwardly extending passage or conduit 86the lower end of which communicates with a generally laterally extendingconduit 88. A downwardly depending conduit 90 communicates at its upperend with conduit 88 and at its lower end with induction passage means 34as through aperture means 92. The effective size of discharge aperture92 is variably established as by an axially adjustable needle valvemember 94 threadably carried by body 32. As generally shown and asgenerally known in the art, passage 88 may terminate in a relativelyvertically elongated discharge opening or aperture 96 located as to begenerally juxtaposed to an edge of throttle valve 52 when such throttlevalve 52 is in its curb-idle or nominally closed position. Often,aperture 96 is referred to in the art as being a transfer sloteffectively increasing the area for flow of fuel to the underside ofthrottle valve 52 as the throttle valve is moved toward a more fullyopened position.

Conduit means 98, provided with calibrated air metering or restrictionmeans 100, serves to communicate as between an upper portion of conduit86 and a source of atmospheric air as at the inlet end 36 of inductionpassage 34.

At idle engine operation, the greatly reduced pressure area below thethrottle valve means causes fuel to flow as from the fuel reservoir 58and well 64 through conduit means 83 and restriction means 82 andgenerally intermixes with the bleed air provided by conduit 98 and airbleed restriction means 100. The fuel-air emulsion then is drawndownwardly through conduit 86 and through conduits 88 and 90 ultimatelydischarged, posterior to throttle valve 52, through the effectiveopening of aperture 92.

During off-idle operation, the throttle valve means 52 is moved in theopening direction causing the juxtaposed edge of the throttle valve tofurther effectively open and expose a greater portion of the transferslot or port means 96 to the manifold vacuum existing posterior to thethrottle valve. This, of course, causes additional metered idle fuelflow through the transfer port means 96. As the throttle valve means 52is opened still wider and the engine speed increases, the velocity ofair flow through the induction passage 34 increases to the point wherethe resulting developed venturi vacuum is sufficient to cause thehereinbefore described main metering system to be brought intooperation.

The invention as herein disclosed and described provides means, inaddition to those hereinbefore described, for controlling and/ormodifying the metering characteristics otherwise established by thefluid circuit constants previously described. In the embodimentdisclosed, among other cooperating elements, solenoid valving means 102is provided to enable the performance of such modifying and/or controlfunctions.

The solenoid valving means 102 is illustrated in greater detail in FIG.3 and the detailed description thereof will hereinafter be presented inregard to the consideration of said FIG. 3. However, at this point, andstill with reference to FIG. 2, it will be sufficient to point out that,in the embodiment disclosed, the solenoid means or assembly 102 has anoperative upper end and an operative lower end and that such means orassembly 102 may be carried by the carbureting body means as, forexample, to be partly received by the fuel reservoir 58. As generallydepicted in FIG. 2, the lower operative end of solenoid valving means orassembly 102 is operatively received as by an opening 104 formed as inthe interior of fuel reservoir 58 with such opening 104 generally, inturn, communicating with passage means 106 leading to the main fuel well64. In fact, as also depicted, the idle fuel passage 83 may communicatewith main well 64 through a portion of such passage means 106 which ispreferably provided with calibrated restriction means 108.

The carbureting means 28 may be comprised of an upper disposed body orhousing section 110 provided as with a cover-like portion 112 whichserves to in effect cover the fuel reservoir 58. As also depicted inFIG. 2, the upper end of solenoid assembly 102 may be generally receivedthrough cover section 112 as to have the upper end of assembly 102received as by an opening 114 formed as within a cap-like housing orbody portion 116 which has a relatively enlarged passage or chamber 118formed therein and communicating with laterally extending passages orconduits 120 and 122 which, in turn, respectively communicate withillustrated downwardly extending passage or conduits 124 and 126. Aconduit 128, formed in housing section 110, serves to interconnect andcomplete communication as between the lower end of conduit 124 and theupper end of conduit 86, while a second conduit 130, also formed inhousing section 110, serves to interconnect and complete communicationas between the lower end of conduit 126 and a source of ambientatmosphere as, preferably, at a point in the air inlet end of inductionpassage means 34. Such may take the form of an opening 132,communicating with passage means 34, situated generally downstream ofchoke or air valve means 38.

Referring in greater detail to both FIGS. 2 and 3, and in particular toFIG. 3, chamber 118 of housing portion 116 is shown as having acylindrical passage portion 133 with an axially extending sectionthereof being internally threaded as at 135 in order to threadablyengage a generally tubular valve seat member 137 which has itsinner-most end provided with an annular seal, such as an O-ring, 139thereby sealing such inner-most end of member 137 against the surface ofcylindrical passage portion 133. As depicted, valve seat member 137 isgenerally necked-down at its mid-section thereby providing for anannular chamber 141 thereabout with such annular chamber 141 being, ofcourse, partly defined by a cooperating portion of chamber or passagemeans 118. A plurality of generally radially directed apertures orpassages 143 serve to complete communication as between annular chamber141 and an axially extending conduit 145, formed in the body of valveseat member 137, which, in turn, communicates with a valve seatcalibrated orifice or passage 147. After the valve seat member 137 isthreadably axially positioned in the selected relationship, a suitablechamber closure member 149 may be placed in the otherwise open end ofchamber 118.

The solenoid assembly 102 is illustrated as comprising a generallytubular outer case 151 the upper end of which is slotted, as depicted at153, and receives an upper end sleeve member 155 which may be secured tothe outer case or housing 151 as by, for example, having the end member155 pressed into the housing 151 and then further crimping housing 151against member 155. The outer surface 157 of the upper end of sleevemember 155 is closely received within cooperating receiving opening 114.

A generally lower disposed end sleeve member 159 may be similarlyreceived by the lower open end of case or housing 151 and suitablysecured thereto as by, for example, crimping. Preferably, sleeve member159 is provided with a flange portion 161 against which the end of case151 may axially abut. The lower-most end of sleeve member 159 is closelyreceived within cooperating opening or passage 104 and is provided withan annular groove or recess which, in turn, receives and retains a seal,such as, for example, an "O"-ring, 163 which serves to assure suchlower-most portion of sleeve 159 being peripherally sealed against thesurface of opening 104. A generally medially situated chamber 165,formed in sleeve member 159 is preferably provided with an internallythreaded portion 167 which threadably engages a threadably axiallyadjustable valve seat member 169 which, in turn, is provided with acalibrated valve orifice or passageway 171 effective for communicatingas between chamber 165 and passage or conduit means 106. A plurality ofgenerally radially directed apertures or passages 173 serve to completecommunication as between chamber 165 and the interior of the fuelreservoir 58.

A spool-like member 175 has an axially extending cylindrical tubularportion 177 the upper end 179 of which is closely received within acooperating recess-like aperture 181 provided by upper sleeve member155. Near the upper end of spool member 175, such member is providedwith a generally cylindrical cup-like portion 183 which, in turn,defines an upper disposed abutment or axial end mounting surface 185which abuts as against a flat insulating member 187 situated against thelower end surface 189 of upper sleeve member 155 and about the upperportion 179 of tubular portion 177. An electrical coil or winding 191,carried generally about tubular portion 177 and between axial end walls193 and 195 of spool 175, may have its leads 197 and 199 pass as throughwall portion 193 for connection to related circuitry, to be described.An annular bowed spring 203 is axially contained between end wall 195 ofspool 175 and the upper face 205 of lower sleeve member 159 and servesto resiliently hold the spool and coil assembly (175 and 191) in itsdepicted assembled condition within case or housing 151.

A cylindrical armature 207, slidably reciprocatingly received withintubular portion 177 and aligned passageway 209, formed as in a bushingmember 201 situated in sleeve member 155, has an upper disposed axialextension 211 and an integrally formed annular flange-like portion 217which internally engage and both laterally and axially retain a related,at least somewhat resilient, generally cup-like valve member 213.

Somewhat similarly, the lower end of armature 207 is in operativeabutting engagement with an axial extension, such as a pin or rod 221which passes through a clearance passageway 223, formed in lower sleevemember 159, (including its tubular extension 215 received with tubularportion 177 of spool 175) and abutably engages a lower disposed valvingmember 225 which is provided with an axial extension 219 and integrallyformed annular flange 251 which internally engage and laterally andaxially retain, at least a somewhat resilient, generally cup-like valvemember 227. A compression spring 229 has one end seated as against valveseat member 169 and its other end seated against a suitable flangeportion 231 of valving member 225 as to thereby normally yieldingly urgethe valve member 227 and armature 207 axially away from the valve seatmember 169 (that being the opening direction for valve passageway 171).

As should be apparent, upon energization and de-energization of the coil191, armature 207 will experience reciprocating motion with the resultthat, in alternating fashion, valve member 213 will close and opencalibrated passageway 147 while valve member 227 will open and closecalibrated passageway 171.

Without, at this point, considering the overall operation, it should nowbe apparent that when, for example, armature 207 is in its upper-mostposition and valve member 227 has fully closed passageway or orifice147, all communication between conduits 120 and 122 is terminated.Therefore, the only source for any bleed air, to be mixed with raw orsolid fuel being drawn through conduit means 83 (to thereby create thefuel-air emulsion previously referred to herein), is through bleed airpassage 98 and calibrated bleed air restriction means 100 (FIG. 2). Theratio of fuel-to-air in such an emulsion (under such an assumedcondition) will be determined by the restrictive quality of air bleedrestriction means 100, alone.

However, let it be assumed that armature 207 has moved to its lower-mostposition, as depicted, and that valve member 213 has, thereby, fullyopened calibrated passageway 147. Under such an assumed condition, itcan be seen that communication, via passage or orifice 147, is completedas between conduits 120 and 122 with the result that now, the top ofconduit 86 (FIG. 2) is in controlled (by virtue of the restrictivequalities or characteristics occurring at passageway 147) communicationwith a source of ambient atmosphere via conduits 128, 124, 120, 143,145, 147, 122, 126 and 130 and opening 132 (FIG. 2). Accordingly, it canbe seen that under such an assumed condition the source for bleed air,to be mixed with raw or solid fuel being drawn through conduit means 83(to thereby create the fuel-air emulsion hereinbefore referred to), isthrough both bleed air passage 98 and restriction means 100 as well asconduit means 130 as set forth above. Therefore, it can be readily seenthat under such an assumed condition significantly more bleed-air willbe available and the resulting ratio of fuel-to-air in such an emulsionwill be accordingly significantly leaner (in terms of fuel) than thefuel-to-air ratio obtained when only conduit 98 and restriction 100 werethe sole source of bleed air.

Obviously, the two assumed conditions discussed above are extremes andan entire range of conditions exist between such extremes. Further,since the armature 207 and valve member 213 will, during operation,intermittently reciprocatingly open and close passageway or orifice 147,the percentage of time, within any selected unit or span of time used asa reference, that the orifice 147 is opened will determine the degree towhich such variably determined additional bleed air becomes availablefor intermixing with the said raw or solid fuel.

Generally, and by way of summary, with proportionately greater rate offlow of idle bleed air, the less, proportionately, is the rate ofmetered idle fuel flow thereby causing a reduction in the richness (interms of fuel) in the fuel-air mixture supplied through the inductionpassage 34 and into the intake manifold 26. The converse is also true;that is, as aperture or orifice means 147 is more nearly totally, interms of time, closed, the total rate of idle bleed air becomesincreasingly more dependent upon the comparatively reduced effectiveflow area of restriction means 100 thereby proportionately reducing therate of idle bleed air and increasing, proportionately, the rate ofmetered idle fuel flow and, thereby, resulting in an increase in therichness (in terms of fuel) in the fuel-air mixture supplied throughinduction passage 34 and into the intake manifold 26.

Further, it should also be apparent that for any selected meteringpressure differential between the venturi vacuum, P_(v), and thepressure, P_(a), within reservor 58, the "richness" of the fueldelivered by the main fuel metering system can be modulated merely bythe moving of valve member 227 toward and/or away from coacting aperturemeans 171. That is, for any such given metering pressure differential,the greater the effective opening of aperture 171 becomes, the greateralso becomes the rate of metered fuel flow since one of the factorscontrolling such rate is the effective area of the metering orificemeans. Obviously, in the embodiment disclosed, the effective flow areaof orifice means 171 is fixed; however, the effectiveness of flowpermitted therethrough is related to the percentage of time, within anyselected unit or span of time used as a reference, that the orificemeans 171 is opened (valving means 225 and valve member 227 being movedaway from passage means 171) thereby permitting an increase in the rateof fuel flow through passages 173, 165, 171 and 106 to main fuel well 64(FIG. 2). With such opening of orifice means 171 it can be seen that themetering area of orifice means 171 is, generally, additive to theeffective metering area of orifice means 78. Therefore, a comparativelyincreased rate of metered fuel flow is consequently discharged, throughnozzle 50, into the induction passage means 34. The converse is alsotrue; that is, the less that orifice means 171 is effectively open oropened, the total effective main fuel metering area effectivelydecreases and approaches that effective area determined by meteringmeans 78. Consequently, the total rate of metered main fuel flowdecreases and a comparatively decreased rate of metered fuel flow isdischarged through nozzle 50 into the induction passage 34.

Referring again to FIG. 1, it can be seen that suitable vehicular speedsensing means 23 may be operatively connected to the engine power outputtrain, as, for example, to the output or drive shaft means 13. The speedsensing means 23 is of the type which senses the speed of rotation and,in turn, produces an electrical output signal, as along conductor means25, 27, which is of a magnitude reflective of such sensed speed. Such aspeed signal is then applied, as an input signal to the control andcomputer means 29 which may be powdered as by a suitable source ofelectrical potential 31 indicated as being grounded as at 33.

Although the practice of the invention is not limited to any specificform or embodiment of a control and computer means 29, it has beendiscovered during testing of the invention that a commercially availableapparatus designated as a "ZT3 Driving Computer" and sold by Zemco, Inc.of 12907 Alcosta Blvd., San Ramon, Calif., U.S.A. (and also described ina publication captioned ZT3 DRIVING COMPUTER and bearing a copyrightnotice of 1980 by Zemco, Inc.) provides acceptable performance. Further,as will become apparent, such a commercially available control andcomputer 29 may be modified as by the incorporation or the additionthereto of circuit means employing teachings of the invention and asgenerally depicted in FIG. 6. That is to say, in the present disclosure,it is assumed that the means 29, as depicted in FIG. 1, includes thecircuit means of FIG. 6 or the functional equivalent thereof. However,that is not to mean that the invention is limited to such a combinationsince the various circuits and computer means may actually be physicallyseparated from each other and only operatively interconnected.

Similarly, even though the practice of the invention is not limited tothe use of any specific form or embodiment of a speed sensing means 23,it has been discovered during testing of the invention that acommercially available apparatus designated as a portion of an overallkit comprising said "ZT3 Driving Computer" provides acceptableperformance.

Still referring to FIG. 1, a vehicular fuel tank 35 is shown supplyingfuel as via conduit means 37 to the inlet of an associated fuel pump 39which, in turn, pumps such fuel as via conduit means 41 to the inlet 59(FIG. 2) of the fuel reservoir 58 of carbureting means 28. A flow sensormeans 43, illustrated as comprising a portion of the conduit means 41,senses the rate of flow, per unit of time, of fuel to the carburetingmeans 28, and therefore to the engine 10, and in accordance therewithproduces an electrical output signal which is applied as via conductormeans 45 and 47 as an input signal to the control means 29. Again, eventhough the practice of the invention is not limited to the use of anyspecific form or embodiment of a flow sensor means 43, it has beendiscovered during testing of the invention that a commercially availableapparatus designated as a portion of an overall kit comprising said "ZT3Driving Computer" provides acceptable performance. A pair of electricalconductor means 514 and 515 are illustrated as electricallyinterconnecting the control means 29 and carburetor means 28, and, morespecifically, the coil 191 leads 197, 199 of the solenoid valving means102 (FIGS. 2 and 3).

In the preferred embodiment, the control means 29 would comprisesuitable housing means the face of which would carry or provide suitablepush-button means 49, 51, 53, 55, 57, 61, 63, 65 and 67 along with avisual read-out digital display 69. Such push-buttons, when actuated,could result in the digital display providing a read-out of various bitsof information. For example upon actuation of: (a) 49, the display wouldindicate the rate of fuel consumption in terms of miles per gallon, orthe like; (b) 51, the display would indicate the vehicular speed; (c)53, the display would indicate the elapsed time as from, for example,the beginning of a trip (d) 55, the display would indicate the then timeof day; (e) 57, the display would indicate the distance traveled as, forexample, from the start of a trip; (f) 61, the display would indicatethe quantity of fuel consumed as from the start of a trip; (g) 63, thedisplay would indicate the average speed of the vehicle as, for example,from the start of a trip and (h) 65, the associated circuitry anddisplay would be reset.

Also, in the preferred embodiment, the control means 29 would carry amanually adjustable control member 71 as in the form of, for example, arotatable knob which may be provided with a pointer 73 so that as thecontrol knob 71 is rotated the pointer 73 would generally sweep acrossor in respect to radiating graduations 75 with the left-most (as viewedin FIG. 1) thereof being designated as "Rich", or the like, and theright-most (as viewed in FIG. 1) being designated as "Lean", or thelike.

Generally, as is well known, as the vehicle is being operated, thesignals generated and supplied by the speed sensor means 23 and the flowsensor means 43 are integrated by the circuitry of the computer portionof the control means 29 so that, depending upon the function selected asby the actuation of a push-button, the corresponding information ispresented by the digital display 69.

Referring now in greater detail to FIG. 6, control circuit means 160,embodying teachings of the invention, is illustrated as comprising asource of electrical potential, which may be the same source 31 as shownin FIG. 1, grounded as at 33 and having its other terminal electricallyconnected, as through engine ignition switch means 77, to conductormeans 301 and 303. A vacuum responsive electrical switching means 305 isshown as being in series with conductor means 303 which, at its otherend, may be considered as being electrically connected as at juncturemeans 306 to conductor means 307, 308 and 310.

The other end of conductor means 307, which comprises series resistormeans 312, is electrically connected to the base terminal 313 of anN-P-N transistor 314 while the other end of conductor means 308, whichcomprises series resistor means 315, is electrically connected to thebase terminal 319 of a second N-P-N transistor 316. Conductor means 310,illustrated as comprising series resistor means 317, is connected toground potential as at 318.

A first capacitor means 320 has one of its electrical sides electricallyconnected to conductor means 307 as at a point 321 electrically betweenresistor means 312 and base terminal 313 of transistor 314 while itsother electrical side is brought to ground as at 322. Similarly, asecond capacitor means 323 has one of its electrical sides electricallyconnected to conductor means 308 as at a point 324 electrically betweenresistor means 315 and base terminal 319 of transistor 316 while itsother electrical side is brought to ground as at 325.

The collector electrode or terminal 326 of transistor 314 iselectrically connected to conductor means 327 which comprises seriessituated resistance means 328, 329 and 330 while the emitter electrodeor terminal 331 of transistor 314 is electrically connected to conductormeans 332 which comprises series situated resistance means 333, 334 and335. Conductor means 327 and 332 may be electrically joined as at 336and, in turn, electrically coupled as via conductor means 337 to thebase terminal 420 of a Darlington circuit 410 which comprises N-P-Ntransistors 412 and 414. The emitter electrode 422 of transistor 414 isconnected to ground as at 424 while the collector 425 thereof iselectrically connected as by conductor means 426 connectable, as at 428and 430, to the solenoid means 102, and leading to the related source ofelectrical potential as by, for example, electrical connection throughconductor means 303.

The collector 434 of transistor 412 is electrically connected toconductor means 426, as at point 436, while the emitter 438 thereof iselectrically connected to the base terminal 440 Of transistor 414.Preferably, a diode 442 is placed in parallel with solenoid means 191.Although not essential to the practice of the invention, alight-emitting diode 444 may be provided to visually indicate thecondition of operation.

A first operational amplifier 338 is illustrated as having its invertinginput terminal 339 electrically connected as via conductor means 340 toone electrical side of capacitor means 341 the other electrical side ofwhich is connected as via conductor means 342 to ground as at 343. Thepositive (+) terminal 345 of amplifier 338 is also connected to ground343 as through conductor means 344 comprising series resistance means346.

Conductor means 301, which may comprise suitable series situatedresistance means 347, is electrically connected to conductor means 327as at a point 348 generally on the collector 326 side of resistancemeans 328. An internal power supply conductor means 349 is electricallyconnected as between terminal 350 of amplifier 338 and conductor means301 as at a point 351 thereof. A zener diode 352, grounded as at 353,may also be connected to point 351 as to thereby regulate the potentialat points 351 and 348 as well as across the amplifier terminals 350 and354 with terminal 354 being grounded as at 355.

The output terminal 356 of amplifier 338 is connected as by conductormeans 357 to conductor means 358 which, at its lower end is connected toconductor means 327 as at a point 359 electrically between resistancemeans 329 and 330, and which at its upper portion (as viewed in FIG. 6)is connected to what may be considered a looped conductor means 360 asat points 361 and 362. In the preferred embodiment, conductor means 360comprises series situated: diode 363, resistance means 364,potentiometer resistance means 365, resistance means 366 and diode means367. The potentiometer wiper contact 368, positioned as by the manualcontrol knob 71, is electrically connected, as via conductor means 369,to inverter input terminal 339 as by its connection to conductor means340 as at a point 370 generally electrically between capacitor means 341and terminal 339.

The collector 371 of transistor 316 is electrically connected to thepositive input terminal 345 of amplifier 338 and to conductor means 327as by conductor means 372 and 373 wherein conductor means 373 may haveone end connected to conductor means 344, as at a point 374 thereofgenerally electrically between resistance means 346 and terminal 345,and may have its other end connected to conductor means 327 as at apoint 375 thereof generally electrically between resistance means 328and 329. The emitter 376 of transistor 316 is brought to ground as at377.

A second operational amplifier 378 has its positive input terminal 379electrically connected as to conductor means 380, comprising seriesresistance means 381, leading to ground as at 382. The inverting inputterminal 383 of amplifier 378 is electrically connected as by conductormeans 384 to one electrical side of capacitor means 385 which has itsother electrical side connected as via conductor means 386 and 380 toground 382. A conductor means 387 serves to electrically interconnectinput terminal 379 and conductor means 332 as by having its oppositeends respectively connected to conductor 332, as at a point 388 thereofgenerally electrically between resistance means 333 and 334, and toconductor 380, as at a point 389 thereof generally electrically betweenterminal 379 and resistance 381.

The output terminal 390 of amplifier 378 is electrically connected, asvia conductor means 391, to conductor means 392 which has its one endelectrically connected to conductor means 332 as at a point 393 thereofgenerally electrically between resistance means 334 and 335. The otherend, generally, of conductor 392 is connected as to conductor means 394and 395 which respectively comprise diode means 396 and resistance means397, and, diode means 398 and resistance means 399. The other respectiveends of conductor means 394 and 395 are each electrically connected tothe inverting input terminal 383 as by conductor means 400 which isillustrated as being electrically connected to conductor means 384 as ata point 401 thereof generally electrically between terminal 383 andcapacitor means 385.

As depicted, suitable zener diode means 402 may be provided as toregulate the potential across 191 and as across point 306 to points 377and 424.

In one successful embodiment of the circuit means of the invention asshown in FIG. 6, the following elements had the respectively indicatedvalues:

Resistor 312: 100 K

Resistor 315: 100 K

Resistor 317: 100 K

Resistor 328: 1.0 Meg.

Resistor 329: 1.0 Meg.

Resistor 330: 27 K

Resistor 333: 1.0 Meg.

Resistor 334: 1.0 Meg.

Resistor 335: 27 K

Resistor 364: 200 K

Resistor 365: 1.0 Meg.

Resistor 366: 200 K

Resistor 346: 1.0 Meg.

Resistor 381: 1.0 Meg.

Resistor 397: 200 K

Resistor 399: 2.5 Meg.

Capacitor 320: 0.01 μf

Capacitor 323: 0.01 μf

Capacitor 341: 0.10 μf

Capacitor 385: 0.047 μf

The integrated circuit portions or amplifiers 338 and 378 actuallycomprised type LM358 (low power dual operational amplifiers)manufactured by National Semiconductor Corp. of 2900 SemiconductorDrive, Sant Clara, Calif., U.S.A. and described as at Page 3-148 of thepublication entitled "Linear Data Book" and bearing a U.S. of Americacopyright notice of 1978 by National Semiconductor Corp. If furtherclarification is desired, terminals 390, 383, 379, 354, 345, 339, 356and 350 correspond respectively to pins of terminals 1, 2, 3, 4, 5, 6, 7and 8 of the dual amplifier as depicted in the "connection diagrams"appearing on said Page 3-148 of said publication "Linear Data Book".Diodes 363, 367, 396, 398 and 442 each were of the type 1N4001;transistors 314 and 316 were each equivalent of the type 2N4124manufactured by Texas Instruments Incorporated of Dallas, Tex., U.S.A.,and as described as at Page 4-318 of the publication entitled "TheTransistor and Diode Data Book", first edition, and bearing a U.S. ofAmerica copyright notice of 1973 by Texas Instruments Incorporated. TheDarlington-connected transistors 412 and 414 were equivalent of the type2N5525 manufactured by the said Texas Instruments Incorporated andappearing as on Page 4-422 of said publication "The Transistor and DiodeData Book".

As should be apparent resistance means 364, 365 and 366, amplifier 338,capacitor 341, resistance means 346, resistance means 329 and associatedconductor means define an oscillator means wherein resistances 364, 365and 366 generally collectively cooperate to define feedback resistancemeans the value of which can be adjustably selected by the wiper contact368 of the potentiometer means.

Generally, two different situations will exist in the circuit means ofFIG. 6. That is, one will exist when the ignition switch means 77 isclosed and the vacuum switch means 305 is open while the other operatingcondition will exist when the ignition switch means 77 and the vacuumswitch means 305 are both closed.

Considering first the operating condition wherein ignition switch meansis closed but vacuum switch means 305 is opened, it will be seen thatground potential will exist at point 306 because of its connection toground 318 as by resistor means 317. At this time transistors 314 and316 are each in a non-conducting state ("off") because the groundpotential of point 306 is applied via conductor means 307 and 308 to thebase terminals 313 and 319 of transistors 314 and 316, respectively.

Since there is, at this time, no positive voltage being fed from or atemitter 331 of transistor 314, the operational amplifier 378 does notreceive the needed positive reference voltage for the non-invertinginput terminal 379 thereof and, therefore, the operational amplifier 378is rendered effectively non-operating and no output is produced atoutput terminal 390 of amplifier 378.

However, because of the closure of switch means 77, a positive referencevoltage is supplied via conductor means 301 to point 348 and such is, inturn, supplied from point 348 by means of resistor 328 to thenon-inverting input terminal 345 of operational amplifier 338. Such areference voltage is supplied as via conductor means 373 to terminal 345and not brought to ground 377 because, at this time, transistor 316 isoff. Consequently, the first oscillator circuit means causes theproduction of outputs at output terminal 356.

The first oscillator circuit means comprises resistance means 364, 365and 366, capacitor 341 and operational amplifier 338. Generally, theoutput at terminal 356 will be either ground potential ("low") or up tosupply voltage as, for example, 12.0 volts ("high").

Assuming now, for purposes of illustration, that the output at terminal356 is "high", current flows from output terminal 356 through diode 363,resistor 364, potentiometer 365, wiper 368, conductor 369, capacitor 341and conductor 342 to ground 343 thereby charging the capacitor 341.During such charging time the "high" voltage output is also applied viaresistor 330 and conductor 337 to the base 420 of Darlington 410 causingthe Darlington to go into conduction resulting in the energization ofcoil 191.

Once the capacitor 341 is sufficiently charged so that the potential onthe inverting input terminal 339 starts to exceed the magnitude of thereference voltage at the non-inverting terminal 345, the operationalamplifier 338 is effectively switched and the output at terminal 356thereof becomes "low" resulting in the removal of the forward bias onthe base 420 of Darlington 410 causing the Darlington 410 to becomenon-conductive and consequently de-energizing the solenoid coil. At thesame time, the capacitor 341 starts to discharge through the dischargingpath comprised of conductor 369, wiper 368, potentiometer 365,resistance 366 and diode 367. Such discharging continues until thepotential of the inverting input 339 becomes lower than the potential ofthe non-inverting input terminal 345 and, at that time, the operationalamplifier 338 will again be effectively switched and the output atterminal 356 will again become "high" resulting in the repeating of thecycle by again charging capacitor 341.

Now, considering the second condition of operation wherein both switchmeans 77 and 305 are closed, it will be seen that positive voltage fromconductor 303 is applied, via conductor means 307 and 308, to baseterminals 313 and 319 of transistors 314 and 316, respectively, causingeach transistor 314 and 316 to become conductive and, as will be seen,causing the said first oscillator means to become effectivelyinoperative while making a second oscillator means operative. The secondoscillator means comprises resistor means 397 and 399, capacitor 385 andoperational amplifier 378.

In such second condition of operation with both transistors 314 and 316being conductive, points 374 and 375 are brought effectively to groundpotential via conducting transistor 316, while points 388 and 389 arebrought effectively to high positive supply voltage as via point 348 andconducting transistor 314.

As a consequence of point 374 being brought to ground potential, thenon-inverting input terminal 345 of amplifier 338 has no reference inputand therefore the amplifier 338 is rendered effectively non-operativeand produces no output as at terminal 356.

However, because of points 388 and 389 being brought to high positivevoltage, the non-inverting input terminal 379 of amplifier 378 has therequired reference input supplied thereto. This, in turn, results in thesaid second oscillator means producing outputs at 390 of amplifier 378.

Generally, the output at terminal 390 of amplifier 378 will be eitherground potential ("low") or up to supply voltage, as for example, 12.0volts ("high").

Assuming now, for purposes of description, that the output at terminal390 is "high", current flows from output terminal 390 through diode 396,resistor 397, capacitor 385 and conductor 386 to ground 382 therebycharging capacitor 385. During such charging time the "high" voltageoutput is also applied via resistor 335 and conductor 337 to the base420 of Darlington 410 causing the Darlington to go into conduction andenergizing solenoid coil 191.

Once the capacitor 385 is charged so that the potential on the invertinginput terminal 383 starts to exceed the magnitude of the referencevoltage at the non-inverting terminal 379, the operational amplifier 378is effectively switched and the output at terminal 390 thereof becomes"low" resulting in the removal of the forward bias on the base 420 ofDarlington 410 causing the Darlington 410 to become non-conductive andconsequently de-energizing the solenoid coil 191. At the same time, thecapacitor 385 starts to discharge through the discharging pathcomprising resistor 399 and diode 398. Such discharging continues untilthe potential of the inverting input terminal 383 becomes lower than thepotential of the non-inverting input terminal 379 and, at that time, theoperational amplifier 378 will again be effectively switched and theoutput at terminal 390 will again become "high" resulting in therepeating of the cycle by again charging capacitor 385.

Accordingly, it should now be apparent that during the first conditionof operation, wherein outputs are produced by amplifier means 338, thelength of time that solenoid coil means 191 is energized is a functionof the charging time of capacitor means 341 through resistance means364, potentiometer 365 and wiper 368 while the length of time thatsolenoid coil means 191 is de-energized is a function of the dischargingtime of capacitor 341 through wiper 368, potentiometer 365, resistance366 and diode 367.

It should also be apparent that during the second condition ofoperation, wherein outputs are produced by amplifier means 378, thelength of time that solenoid coil means 191 is energized is a functionof the charging time of capacitor means 385 through diode 396, andresistance means 397 while the length of time that solenoid coil means191 is de-energized is a function of the discharging time of capacitor385 through resistance means 399 and diode 398.

With respect to the said second oscillator means, the frequency andpercentage of time that a "high" output is, produced are fixed in thatthe resistance values of resistance means 397 and 399 are fixed.However, with respect to the said first oscillator means, the percentageof time that a "high" output is produced at terminal 356 is variable bythe provision of the potentiometer means comprised of potentiometerresistance 365 and wiper 368. Accordingly, it is apparent that withadjustment of the potentiometer wiper 368 generally counter-clockwise asviewed in FIG. 6 that the percentage of time that a "high" output isproduced at 356 will decrease and consequently the percentage of timethat solenoid coil means 191 is energized will be correspondinglyreduced while the percentage of time that a "low" output is produced at356 and the percentage of time that solenoid coil means 191 will bede-energized will increase. In like manner, if the potentiometer wiper368 is selectively adjusted generally clockwise as viewed in FIG. 6, thepercentage of time that a "high" output is produced at 356 and thepercentage of time that solenoid coil means 191 will be energized willincrease while the percentage of time that a "low" output is produced at356 and the percentage of time the solenoid coil is de-energized willdecrease.

In the structure as depicted in FIG. 3, it is clear that valving member227 will be seated and closing fuel flow through passage means 171 onlywhen solenoid winding 191 is energized, and, as already hereinbeforeexplained, energization of the winding or coil 191 occurs only when andduring the time that the output of either amplifier 338 or 378 is"high". In the preferred embodiment of the invention, the valuesselected in the said first oscillator circuit means are such as toenable a selection of from 30 percent to 80 percent duty cycle. That is,in the overall cycle time of the first oscillator circuit means, theoutput at 356 would be "high" (and solenoid winding 191 would beenergized) anywhere (selectively) from 30 to 80 percent of such cycletime. Also, in the preferred embodiment of the invention, the circuitconstants of the said second oscillator circuit means are such as toproduce a 10 percent duty cycle. That is, in the overall cycle time ofthe second oscillator circuit means, the output at 390 would be "high"(and solenoid winding 191 would be energized) during 10 percent of suchcycle time.

Further, as generally depicted in FIG. 6, the pressure responsive means540 of the vacuum responsive switch means 305 is operatively connectedas via conduit means 542 to a source of engine intake manifold vacuum asthrough cooperating passage means 544 (FIG. 2).

Coil 191 leads 197 and 199 (FIG. 3) may pass through suitable clearanceor passage means 500 and 502 (FIG. 4) and pass through relieved portions504, 506 (formed as in integrally formed arm portion 512) and then berespectively received as within eyelets 508, 510 which also respectivelyreceive enlarged conductor extensions of such leads 197 and 199 (one ofsuch being partly depicted at 514 in FIG. 3). Such extensions may, ofcourse, be brought out of the carburetor housing means in any suitablemanner as to thereby, in effect, respectively comprise the conductormeans 197 and 199 as depicted in FIG. 6.

OPERATION

Referring in particular to both FIGS. 2 and 3, it can be seen that whensolenoid coil 191 is energized causing the valving element 227 to beseated, closing passage means 171, the upper disposed valving element213 is moved fully away from its seated engagement and fully openingpassage 147. In this position of the valving means fuel flow throughmain fuel passage means 171 is terminated while maximum flow of idlefuel bleed air is permitted. Such bleed air flow occurs as from inlet132 (FIG. 2), through conduit means 130, conduit means 122, passagemeans 147, 145, passage or aperture means 143, conduit means 120, 124and 128 and a portion of conduit means 86. Such, of course, is inaddition to the bleed air flow provided via conduit means 98. This, ofcourse, results in the leanest (in terms of fuel) idle fuel flow beingmetered to the engine.

In comparison, when solenoid coil 191 is de-energized, spring means 229moves valving element 213 upwardly as to be seated closing passage 147while at the same time moving valving element 227 fully away frompassage 171 thereby fully opening passage 171 and allowing the maximumrate of metered main fuel flow therethrough. Because of the closure ofpassage 147 by valving element 213, the rate of flow of idle bleed airis reduced to a minimum with such being determined by the meteringaction through passage means 98 (FIG. 2). This, of course, results inthe richest (in terms of fuel) idle fuel flow being metered to theengine.

Accordingly, it can be seen that, during a selected span of time, therichness of the idle fuel flow and of the main fuel flow will dependupon the frequency and/or duration of the energization of solenoid coilmeans 191. That is the greater the percentage of time that coil means191 is energized the leaner, in terms of fuel, is the fuel-air ratiodelivered to the engine and the lesser the percentage of time that coilmeans 191 is energized the richer, in terms of fuel, is the fuel-airratio delivered to the engine.

Now assuming the vehicle is being operated under generally normalroad-load conditions (at this time, of course, ignition switch 77 isclosed and vacuum operated switch means 305 is open), the vehicleoperator may actuate the appropriate pushbutton on the device 29 toobtain a read-out at the display 69 indicating the then miles-per-gallonbeing obtained. The vehicle operator may then turn the control knob 71,for example, counterclockwise (to a more richer fuel-air mixture) asviewed in either FIG. 1 or 6, and observe the miles-per-gallon read-outto see if the fuel economy of the vehicle (engine) improves ordecreases. If an improvement in the fuel economy is observed, furtheradjustment in that same direction may be continued until a maximumimprovement is realized. If a decrease in fuel economy is observed, theoperator may, instead, adjust the control knob 71 generally clockwise(to a leaner fuel-air mixture) as viewed in either FIG. 1 or 6, andobserve the miles-per-gallon read-out to see if the fuel economy of thevehicle (engine) improves or decreases. Obviously, if an improvement inthe fuel economy is observed, further adjustment in that same directionmay be continued until a maximum improvement is realized.

Accordingly, it can be appreciated that with the invention a vehicleoperator is, within limits, able to manually select the rate of meteredfuel flow to the engine which will provide the greatest fuel economy forthe then operating conditions. This, of course, means that such factorsas, for example: strong vehicular head winds; varying altitudes ofvehicular operation; heavier vehicle loads as, for example, pulling atrailer or the like; varying ambient temperatures and varying brands andquality of gasoline (or other fuels) may, to a great extent becompensated for during actual vehicle (engine) operation as to obtainmaximum fuel economy.

In the preferred practice of the invention, the various circuitconstants of FIG. 6 as well as the fluid circuit constants of theassociated fuel metering circuits would be selected so that regardlessof whether the vehicle operator adjusts control knob 71 to produce amaximum rich (in terms of fuel) fuel-air ratio supplied to the engine ora maximum lean (in terms of fuel) fuel-air ratio supplied to the engine,the resulting engine exhaust emissions would still be within the limitsset by the governmental authorities. The graph of FIG. 5 generallydepicts fuel-air ratio curves obtainable by the practice of theinvention. For purposes of illustration, let it be assumed that curve200 represents a combustible mixture, metered as to have a ratio of0.068 lbs. of fuel per pound of air. Then, as generally shown, theinvention could (depending upon the degree and direction of adjustmentof knob 71 by the operator) provide a flow of combustible mixtures inthe range anywhere from a selected lower-most fuel-air ratio (forexample, 80 percent duty cycle operation of the said first oscillatorcircuit means) as depicted by curve 202 to a selected upper-mostfuel-air ratio (for example, 30 percent duty cycle operation of the saidfirst oscillator circuit means) as depicted by curve 204. As should beapparent, the invention is capable of providing an infinite family ofsuch fuel-air ratio curves between and including curves 202 and 204. Theportions of curves 202 and 204 respectively between points 212 and 214and points 212, 208 are intended to depict, generally, what may beconsidered as the idle range of operation.

Now, let it be assumed that the vehicle is still operating and that thevehicle operator desires to undergo maximum acceleration as to, forexample, pass another vehicle. As the vehicle operator causes thethrottle valve 52 to, for example, wide open position, the magnitude ofthe intake manifold vacuum decreases and such decreased magnitude, inturn, causes the switch means 305 to close, and as previously described,causing the said first oscillator circuit means to become effectivelyinoperative (no pulsed outputs at 356) and simultaneously causing thesaid second oscillator circuit means to become operative (pulsed outputsat 390). Also as previously described when the said second oscillatorcircuit means becomes operative it has a generally constant, preferably10 percent, duty cycle which provides the richest possible fuel-airratio and, in fuel richness, exceeds the maximum fuel richness which canbe provided by the fuel metering system during the time that the saidfirst oscillator circuit means is operational. In FIG. 5 the curve 218(which may be considered a wide open throttle fuel-air ratio curve) isintended to represent the fuel-air ratio deliverable during such aconstant (10 percent) duty cycle operation.

The vacuum responsive switch means 305 is such as to be closed, forexample, whenever the magnitude of the intake manifold vacuum is equalto or less than 6.0 inches of Hg. However, the magnitude of enginevacuum at which switch means 305 closes is, of course, a value which maybe selected to best suit the particular associated engine. Further, eventhough switch means 305 is disclosed as being pressure responsive, itshould be apparent that other means (not pressure responsive) may beemployed for sensing when, for example, wide open or nearly wide openthrottle engine operation is required or experienced, and, in responsethereto causing closure of switch means 305 as to functionallyinactivate the said first oscillator circuit means and to activate thesaid second oscillator circuit means.

It should also be apparent that the invention may be practiced employingfuel metering means other than that specifically disclosed anddescribed.

Although only a preferred embodiment of the invention has been disclosedand described, it is apparent that other embodiments and modificationsof the invention are possible within the scope of the appended claims.

What is claimed is:
 1. Electrical circuit means for a fuel meteringapparatus for a combustion engine which produces output power as aconsequence of combustion air and fuel being supplied thereto whereinsaid fuel metering apparatus comprises fuel metering means effective formetering fuel to said engine, and wherein said fuel metering meanscomprises electrically operated valving means, said electrical circuitmeans comprising first circuit means for electrically interconnectingsaid electrically operated valving means to a source of electricalpotential, and second circuit means, said second circuit means beingmanually controllable to thereby vary the electrical energization ofsaid electrically operated valving means in order to cause said valvingmeans to meter fuel to said engine in correspondingly varying rates offuel flow based on the rate of air flow to said engine.
 2. Electricalcircuit means according to claim 1 wherein said electrically operatedvalving means comprises solenoid means.
 3. Electrical circuit meansaccording to claim 1 and further comprising third circuit means, saidthird circuit means being effective to vary the electrical energizationof said electrically operated valving means to the degree that the saidvalving means meters fuel to said engine at a rate of flow which resultsin a fuel-air ratio different from the fuel-air ratios attainable bysaid second circuit means.
 4. Electrical circuit means according toclaim 3 wherein said electrically operated valving means comprisessolenoid means.
 5. Electrical circuit means for a fuel meteringapparatus for a combustion engine which produces output power as aconsequence of combustion air and fuel being supplied thereto whereinsaid fuel metering apparatus comprises fuel metering means effective formetering fuel to said engine, and wherein said fuel metering meanscomprises electrically operated valving means, said electrical circuitmeans comprising first circuit means for electrically interconnectingsaid electrically operated valving means to a source of electricalpotential, second circuit means, said second circuit means beingmanually controllable to thereby vary the electrical energization ofsaid electrically operated valving means in order to cause said valvingmeans to meter fuel to said engine in a correspondingly varying rate offuel flow based on the rate of air flow to said engine as to attain atleast a first fuel-air ratio, and third circuit means, said thirdcircuit means being effective to vary the electrical energization ofsaid electrically operated valving means to the degree that the saidvalving means meters fuel to said engine at a rate of flow which resultsin a fuel-air ratio different from the fuel-air ratios attainable bysaid second circuit means, wherein said electrically operated valvingmeans comprises solenoid means, and wherein said second circuit meanscomprises manually adjustable potentiometer means.
 6. Electrical circuitmeans for a fuel metering apparatus for a combustion engine whichproduces output power as a consequence of combustion air and fuel beingsupplied thereto wherein said fuel metering apparatus comprises fuelmetering means effective for metering fuel to said engine, and whereinsaid fuel metering means comprises electrically operated valving means,said electrical circuit means comprising first circuit means forelectrically interconnecting said electrically operated valving means toa source of electrical potential, second circuit means, said secondcircuit means being manually controllable to thereby vary the electricalenergization of said electrically operated valving means in order tocause said valving means to meter fuel to said engine in acorrespondingly varying rate of fuel flow based on the rate of air flowto said engine as to attain at least a first fuel-air ratio, and thirdcircuit means, said third circuit means being effective to vary theelectrical energization of said electrically operated valving means tothe degree that the said valving means meters fuel to said engine at arate of flow which results in a fuel-air ratio different from thefuel-air ratios attainable by said second circuit means, wherein saidelectrically operated valving means comprises solenoid means, andwherein said third circuit means becomes effective upon said engineexperiencing a preselected condition of engine load.
 7. Electricalcircuit means for a fuel metering apparatus for a combustion enginewhich produces output power as a consequence of combustion air and fuelbeing supplied thereto wherein said fuel metering apparatus comprisesfuel metering means effective for metering fuel to said engine, andwherein said fuel metering means comprises electrically operated valvingmeans, said electrical circuit means comprising first circuit means forelectrically interconnecting said electrically operated valving means toa source of electrical potential, second circuit means, said secondcircuit means being manually controllable to thereby vary the electricalenergization of said electrically operated valving means in order tocause said valving means to meter fuel to said engine in acorrespondingly varying rate of fuel flow based on the rate of air flowto said engine as to attain at least a first fuel-air ratio, and thirdcircuit means, said third circuit means being effective to vary theelectrical energization of said electrically operated valving means tothe degree that the said valving means meters fuel to said engine at arate of flow which results in a fuel-air ratio different from thefuel-air ratios attainable by said second circuit means, wherein saidelectrically operated valving means comprises solenoid means, andwherein said third circuit means becomes effective upon said engineexperiencing a preselected condition of engine load, and wherein saidsecond circuit means comprises manually adjustable potentiometer means.8. Electrical circuit means according to claim 7 wherein said secondcircuit means further comprises oscillator means, and wherein adjustmentof said potentiometer means serves to correspondingly adjust theoperation of said oscillator means, said solenoid means being responsiveto the operation of said oscillator means.
 9. Electrical circuit meansaccording to claim 7 wherein said third circuit means comprisesoscillator means, said solenoid means being responsive to the operationof said oscillator means.
 10. Electrical circuit means according toclaim 7 wherein said second circuit means further comprises firstoscillator means, wherein adjustment of said potentiometer means servesto correspondingly adjust the operation of said first oscillator means,said solenoid means being responsive to the operation of said firstoscillator means, said third circuit means further comprising secondoscillator means, said solenoid means being responsive to the operationof said second oscillator means, additional means responsive to theoccurrence of a preselected condition of engine load for rendering saidfirst oscillator means functionally ineffective and causing said secondoscillator means to become effective so that said solenoid means is thenresponsive to only said second oscillator means.
 11. Electrical circuitmeans for a fuel valving means operated by solenoid means, saidelectrical circuit means comprising power circuit means electricallyinterconnecting said solenoid means with a source of electricalpotential, switch means effective for closing and opening said powercircuit means for energizing said solenoid means, first oscillator meanseffective for cyclically causing said switch means to close and open tothereby correspondingly cause cyclic energization of said solenoidmeans, second oscillator means effective for cyclically causing saidswitch means to close and open to thereby correspondingly cause cyclicenergization of said solenoid means, and manually controlled adjustmentmeans for varying the relative percentages of time during which saidfirst oscillator means is effective for causing said switch means to beclosed and open, said second oscillator means being of a constantfrequency and being effective to produce only constant relativepercentages of time during which said switch means is closed and open.12. Electrical circuit means according to claim 11 and furthercomprising second switch means, said second switch means being effectiveto preclude functional operational of said first oscillator means whensaid second oscillator means is operating and to preclude functionaloperation of said second oscillator means when said first oscillatormeans is operating.
 13. Electrical circuit means according to claim 12wherein said second switch means comprises transistor means. 14.Electrical circuit means according to claim 12 and further comprisingthird switch means, said third switch means being effective for causingsaid second switch means to be opened and closed.
 15. Electrical circuitmeans according to claim 14 and further comprising means responsive tothe attainment of a preselected condition of engine load for opening andclosing said third switch means.
 16. Electrical circuit means accordingto claim 15 wherein said first mentioned switch means comprisestransistor means.
 17. Electrical circuit means according to claim 15wherein said adjustment means comprises potentiometer means. 18.Electrical circuit means according to claim 15 wherein said adjustmentmeans comprises potentiometer means, wherein said first mentioned switchmeans comprises transistor means, and wherein said second switch meanscomprises transistor means.